The head of the press watchdog, Sir Christopher Meyer, has come under fire for taking up a £35,000-a-year post on the board of one the world's largest arms companies, as well as a string of other lucrative directorships.

Meyer, who was until February the British ambassador in Washington, earns more than £155,000 a year chairing the Press Complaints Commission for three days a week.

It is estimated he will earn an additional £100,000 a year from the other boardroom jobs he has picked up since taking the PCC chair last May. These include a directorship at one of Washington's largest financial institutions.

Meyer was offered the PCC job after the previous chairman, Lord Wakeham, was forced to resign after being caught up in the Enron scandal. As well as holding a directorship at Enron, Wakeham was on the board at a number of other companies.

Critics claimed Wakeham's extensive outside commercial interests were not suitable for the chair of the press watchdog because they gave rise to potential conflict of interests.

As a former British ambassador to Washington, Meyer received permission from Foreign Secretary Jack Straw to take up a job last summer with GKN, which sells military helicopters and components worldwide.

Ian Pritchard, of the Campaign Against the Arms Trade, said: 'This is Britain's former ambassador in Washington, who now is one of the most powerful figures in the British media.

'We have concerns that he will use his influence to help a company that sells arms and fuels conflicts worldwide. GKN has been selling military equipment to countries like South Africa that can ill afford to spend money on weapons.'

Documents at Companies House reveal that Meyer has also become a director of Riggs Bank Europe, a subsidiary of one of America's oldest finance houses, Riggs National Corporation. He has also joined the board of the music firm Sanctuary Group.

Meyer defended his board appointments, saying they were all in the public domain and would not detract from his job as chairing the PCC.

He said: 'I am completely committed to my job at the PCC. I am contracted to do three days a week, although at the moment I am doing more than that.'

Meyer told The Observer he had informed the PCC's Board of Finance about his external interests.

Jim Raeburn, the board's secretary and treasurer, said he personally was unaware of what other jobs Meyer was doing, although other people might have been informed. 'As long as he has sufficient time to do his job as the PCC chair then we are not concerned,' he added.